Dynamo-electric machine.



No 794,998. PATENTED JULY 18, 1905.

' F. A. MOTT.

DYNAMO ELECTRIC MACHINE.

APPLICATION FILED NOV. 27, 1903.

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P. A. MOTT. DY NAMO ELECTRIC MACHINE.

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PATENTED JULY 18 1905.

P. A. MOTT.

DYNAMO ELECTRIC MACHINE.

APPLICATION FILED NOV. 27, 1903.

swans-sum a ANDREW u GRAHAM Lu HKiTOI mmr-RAIMHIA wmummm u c Patented July 18, 1905.

V PATENT OFFIC FREDERICK A. MOT'I, OF ERIE, PENNSYLVANIA.

DYNAMO-ELECTRIC MACHINE.

SPECIFICATION" forming part of Letters Patent No. 794,998, dated July 18, 1905.

Application filed November 27, 1903. Serial No. 182,844.

hereinafter fully described, and pointed out in the claims.

The leading features of my invention relate to means for preventing the distortion of the magnetic field in the air-gap and pole-face of dynamo electric machinery caused. by the magnetic effect of currents in the armatureconductors and for independently varying the direction or densitypf the magnetic lines in different parts of the pole-face. While it is intended particularly for use on direct-current generators and motors on which voltage or speed may be varied by changing the field-flux, it can be used on both direct and alternating current generators and motors with good results.

In a direct-current generator or motor 1t is Well known that if the brushes are on the neutral points the magnetism resulting from all of the armature ampere-turns under each pole acts with the useful flux of the field. under one pole-tip and against it under the other,

thus distorting the effective field along the pole-face.

If the brushes are shifted from the neutral points, the armature ampereturns embraced by double the angle of lead of the brushes act in direct opposition to the useful flux, while the balance act at an angle tending to produce distortion, as before. In

practice at the present time it is usual to place reluctance in the path of the cross and the back ampere-turns of the armature by means of highly-saturated pole-tips, highlysaturated armature-teeth, and large airgaps. All of these means increase the relutcance of the path of the useful fluX as well, thus requiring increased field excitation. I am able to secure a path of high reluctance for the flux of the cross ampereturns of the armature and at the same time secure a path of lower reluctance for the useful flux than is now usually obtainable.

The invention is illustrated in the accompanying drawings as follows:

Figure 1 shows a side elevation of a dynamo-electric machine comprising my invention, part of the field-coils being in section to better show construction. Fig. 2 is a side elevation of an alternative construction. Fig. 3 is a section on the line 3 3 in Fig. 2. Fig. 4 shows a field-piece of an alternative construction, the windings being in section to better show construction. Fig. 5 is also a field-piece of an alternative construction, the field-windings being in section to better show construction. Fig. 6 shows an alternative construction wherein the rotating field is used, the windings being in section to better show construction.

In Fig. 1 is shown a dynamo-electrical machine with an armature A, commutator B, and brushes 0 of any preferred type used in connection with a special field frame, as follows: D is an outerframework and part of the magnetic circuit. (1 d are pole-tip pieces, of steel or iron, bent or cast to form continuous and laminated parts forming magnetic circuits independent from armature air-gap to armature air-gap, as shown. These are secured to the field-frame D and to each other by means of the non-magnetic rings D or in any substantial manner. The main polepiece at the center is excited by the fieldcoils D and the pole-tip portion by the field coils D the coils on the pole-tip portion be' ing connected in proper sequence to produce poles of alternate sign surrounding the armature through the rheostat d and the coils D on the main pole being connected in like manner with pole-changing switch (i and rheostat d", forming an independent circuit, both of said connections, as indicated by the rheostat, providing shunt-circuits. The passage of a current through the field-coils produces a flux through the magnetic circuit of the machine, as indicated by the dotted lines E E in the upper part of Fig. 1. The passage of a current through the armature tends to set up a flux in the direction indicated by the dotted line F. It will be noted that the air spaces or gaps G are in the paths of these l'luxes produced by the cross ampere-turns of the armature, and their reluctances can be made sulliciently large to practically eliminate all of the evil el'l'ects of the cross ampere turns. It will also be noted that these air-spaces G in no way interfere with the path of the main or effective flux produced by the current in the field-winch ings.

In Fig. 2, A marks the armature, B the commutator, and C the brushes. In this the :fieldframe D has the pole-pieces D, which are formed of the laminations d and d". The field-winding D is around the entire fieldpiece, and consequently excites all the laminations of the pole-piece. An axuiliary winding D is arranged on the laminzc (1", so that they maybe independently excited. In these devices the main polepiece formed by the laminae (1 (1 cannot be excited independently of the laminze d" d, forming the poletips, as in the preferred construction shown in Fig. 1.

Fig. 4 shows another method of placing the field-coils. Here the inner cell I) excites the inner lamination d", which crosses the outer lamination d and terminates at the pole-tips, while the outer coil d excites the entire pole.

It is evident that if the coil D" alone is ac tive the pole-tips alone will be magnetized with the proper magnetic polarity and the flux will reverse through lamina (1 cl, so that although the pole tips be ol necessary strength to produce good commutation the elcctromotive :lorce generated thereby will be opposed by a reverseelcctromotive Force at the pole center, thereby producing a very low resultant voltage, with good commutation in case of a generator of high speed and with good commutation in case of a motor.

For special cases where it might be desirable to entirely eliminate the ellect of the cross ampere turns over the entire polefaces a construction similar to Fig. 5 would be used. Thin sheet iron or steel pieces (1 are separated by air-gaps or sheets of other non-magnetic material and bent to l orm the licld-yoke and pole-pieces. A coil D excites the entire pole.

Fig. 6 shows the same principle applied to a machine with a revolving field, ol which the ligure shows one po.l.epicce 'l'orm ed of laminations (1*. The field is mounted on the shal't I) and is excited by the coil D.

It is evident that in a direct-current generator or motor constructed on the principles above set forth the brushes may remain in practically the neutral position at all loads, as the distribution of the lines of force cannot be changed materially by the armature reaetion. The brushes being in the neutral position, there will be no back ampere-turns to act in opposition to the useful llux, and the excitation can be reduced to a minimum. The armature air-gap can be reduced to that required For mechanical clearance, thus again saving energy in excitation. In a motor the useful flux through the armature can be varied by means oi resistance in the fieldcircuit or otherwise changing the licld am pere-turns from a great amount to a very small amount, with resulting increase in speed. of the armature, and although the armature may be carrying full-load current there will. be practically no fieldv distortion, and good. commutation can be maintained even with a weak field without shift of brushes. 'F or greater variation of speed the center portion. of the pole only would he demagnetized (see Fig. I) and its polarity reversed by means of pole-changer d, so as to generate an electromotive force in the armature opposing the counter electromotive 'l orce caused by the pole-tip flux. By this method any speed can be obtained without changing the density at the pole-tips. In alternating generzttors and motors the forms of field-rings and poles shown and described (particularly in Figs. 5 and 6) will serve, as in direct-current machinery, to prevent distortion ol the magnetism in the pole-faces by the current in the armature, thus tending to maintain the sinowave of eleetromotive force and current which is desirable.

The armatures of any 01 the nmehines described may be rotated in. either direction. with the advantages above set forth.

WVithout limiting myself to the prec sc details of construction shown and decribcd, which may be varied without departing from the spirit of the invention, what I do claim, and desire to secure by Letters Patent, is-

1. In a dy1lame-electric machine, the combination with the armature; of a field comprising a two-part polepiece, said parts being separated by paths of high reluctance; windings for exciting said. pole-piece; and means for varying the current in the winih ings on one of said parts independently of the windings on the other of said parts.

2. In a ('lyi'iamo-electric machine, the combination. with the armature; of a field comprising a two-part pole-piece, said parts be ing separated by paths of high .rcluchtnee; slumt-windings for exciting said polc-picce; and means for varying the current in the windings on one of said parts independi-mtly of the windings on the other of said. parts.

3. In a dynamo-electric machine the combination with the armature; of a field. comprising a two-part pole-piece; shunt-windings for exciting said pole-piece; and means for varying the current in. the windings on.

one of said parts.

4:. In a dynamo-electric machine the combination of the armature; a licld conlprising a two-part pole-piece; means for OXL 'ting one of the parts independently of the other part; and means for reversing the flux in one of the parts. i

5. In a dynamo-electric machine, the combination of the armature; a field comprising two-part pole-piece; means for exciting said parts independently; and means for reversing the flux in one of said parts.

6. In a dynamo-electric machine the combination of the armature; a field comprising two-part pole-pieces, the parts of one polepiece being independently connected with parts of another pole-piece; and means for exciting one of said parts of a pole-piece independently of another of said parts.

7. In a dynamo-electric machine the combination of the armature; a fieldcomprising two-part pole-pieces, the parts of one polepiece being independently connected with parts of another pole-piece; and means for exciting said parts independently.

8. In a dynamo-electric machine the combination of the armature; a field comprising a main pole-piece connected with pole-pieces of different sign at both sides of the main pole pieces; and separate pole tip pieces forming part of the face with the main polepiece and independently connected with polefaces of a different sign; and means for exciting one of said pole-pieces independently of the other.

9. In a dynamo-electric machine the combination of the armature; a field comprising a main pole-piece connected with ole-pieces of different sign at both sides 0 the main pole-piece; separate pole-tip pieces forming part of the face with the main pole-piece and independently connected with pole-faces ofa different sign; and means for exciting said pole-pieces independently.

10. In a dynamo-electric machine the combination of the armature; a field comprising two-part pole-pieces, the parts of one polepiece being independently connected with parts of another pole-piece; means for exciting one of said parts of a pole-piece independently of another -of said parts; and means for reversing the fiux in one of said parts. I

1 1. In a dynamo-electric machine the combination of the armature; a field comprising two-part pole-pieces, the parts of one polepiece being independently connected with parts of another pole-piece; means for exciting said parts independently; and means for reversing the flux in one of said parts.

12. In adynamo-electric machine the combination of the armature; a field comprising a main pole-piece connected with pole-pieces of different sign at both sides of the main pole-piece; and separate pole-tip pieces forming part of the face with the main pole-piece and independently connected with polefaces of a different sign; means for exciting one of said pole-pieces independently of the other; and means for reversing the flux in one of said pole-pieces.

13. In a dynamo-electric machine the combination of the armature; a field comprising a main pole-piece connected with pole-pieces of different sign at both sides of the main pole-piece; separate pole-tip pieces forming part of the face with the main pole-piece and independently connected with pole-faces of a different sign; means for exciting said polepieces independently; and means for reversing the fiux in one of said pole-pieces.

14. In adynamo-electric machine the combination of the armature; a field comprising a main pole-piece connected with pole-pieces of different sign at both sides of the main pole-piece; separate pole-tip pieces forming part of the face with the main pole-piece and independently connected with pole-faces of a different sign; means for exciting one of said pole-pieces independently of the other; and means for reversing the flux in the main polepiece.

15. In a dynamo-electric machine the combination of the main fieldpiece D; the poletip pieces D having the lamination d d windings D for the main pole-pieces D; the poles D being connected both ways with poles of different sign; and the pole-tip pieces D forming the pole tips of two different poles; the winding D arranged on the poletip pieces D between the poles; and means for reversing the flux in the main pole-piece D.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

FREDERICK A. MOTT. IVitnesses:

WILLIS E. OADWELL, M. O. SULLIVAN. 

